The most common way for data centers to have the electricity they need to function is simply to be connected to their local or national power grid. Depending on the country, these grids will provide them with electricity created by an energy mix they won’t master, however green they want to be and no matter how eager they are to reduce their carbon footprints.
This simple truth — that data centers mainly rely on the grid to get energy — is also the clear reason why all of them have to install backup energy too. Matter-of-factly, there is no grid to be reliable enough to match the availability requirement for the highly critical activity of any data center — simply put, no grid is on 100% of the time.